My Fat Cat is Officially On a Diet

It Is a Lot More Complicated Then You Might Think

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Teebee oozing over the side of one of her cat trees

My sweetheart of a cat Teebee has been overweight for going on five years now. As I think back now and try to pinpoint the exact time when she went from normal sized to plus sized I can’t do it. It happened so slowly, it felt like one day I just looked at her, and all of a sudden she was fat. I never fed her table scraps (people food), and she never showed any interest in eating any, but I did obviously give her way too much cat food. I think it was the one thing she knew she could always use to get my attention. Her ‘I am hungry feed me’ act was/is one of the cutest and most irresistible things I have ever seen, and it has been very difficult resisting her charms to keep her current diet on track. That said, so far so good and it has been exactly three weeks now of perfect adherence to her professionally/scientifically designed diet plan.

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Teebee got back

My good friend Kat happens to be a breeder of orientals and when it comes to cats, knows it all. She was more than happy to help when I mentioned my struggles with Teebee’s weight and desire to get her back to a healthy size. As it turns out planning for a cat (or dog) diet is not as simple as it might seem at first blush. Especially for cats, too rapid weight loss can be very dangerous and can result in a disease process known as hepatic lypodosis. This is a life threatening condition in which the liver begins to break down, and once it begins can quickly become irreversible. Because of this it is imperative that you talk to a vet before starting your cat or any companion animal on any sort of diet with the intention of weight loss.

A healthy weight for any animal depends greatly on their particular life stage and several other factors. Kat informed me that before I could put Teebee on a diet I would need to first determine her resting energy requirement (RER) at her current weight. This is the amount of energy needed by a particular animal to perform the essential body functions like digestion, respiration, heart functions, brain functions, etc. The RER is expressed in calories and tells you the number of calories you need to feed your cat or dog each day to meet its basic energy needs. It is calculated by multiplying the animal’s body weight in kilograms raised to the ¾ power by 70. (Of course I am dying to dig into the science behind this curious equation but I have not had the time as yet. In my experience any equation with a factor raised to a fractional power is an equation worth learning more about. Look for an update to this post at some future date with all the gory details).

The RER is then multiplied by factors to estimate the pet’s total daily energy needs, or daily energy requirement (DER). These factors vary depending on the particular situation (life stage, nutritional goal, etc.). In my case the goal was weight loss, and for weight loss in cat’s the multiplicative factor is 0.8. The the original calculated RER value is lessened by 20% to determine the DER, and feeding the cat in question that many calories per day will result in weight loss at a safe rate. Individual pet needs can vary by as much as 50% from calculated values however, so these are only starting points for estimating the amount of food to be provided daily. The calculated amount typically needs to be adjusted up or down as needed to maintain a healthy body condition score and/or muscle condition score. The body condition score can be determined by reference to some very easy to use charts that are widely available online. The muscle condition score is a bit trickier and typically requires a visit with a vet.

The last step in this process is to determine the number of calories per cup (or whatever unit of measure you desire) in the particular food you are feeding your cat and adjust the serving size per day to meet the calculated weight loss DER. I do not intend to wade into the cat food brand/type battle in this post. Suffice to say there are an ungodly number of varieties and brands available many of which are marketed as “weight loss” or “healthy weight” formulations. The calculated DER value however is agnostic as to food type, and treats all calories as equal. Therefore, in theory, no matter the food you are feeding your cat they will lose weight (slowly and healthily) if all you calculations are correct, and you can stick to the program of feeding they indicate. This is of course the hardest part but so far so good for Teebee and I. I will update in a few months with her progress. For reference she started day one of her diet at 17.5 lbs. That is one fat cat.

Written by

Research scientist (Ph.D. micro/mol biology), Thought middle manager, Everyday junglist, Selecta (Ret.), Boulderer, Cat lover, Fish hater

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